Progressively flooding trawl doors



Nov. 1, 1966 F. J. LUKETA 3,281,980

PROGRESSIVELY FLOODING TRAWL DOORS Original Filed Aug. 24, 1962 4Sheets-sheet l JNVEN TOR. EQA/V/d J 104 57 V- 1966 F. J. LUKETAPROGRESSIVELY FLOODING TRAWL DOORS 4 Sheets-Sheet 2 Original Filed Aug.24, 1962 INVEN TOR. MFA 1W4 M Awe H94 ava; A rro/P'A/n s' Nov. 1, 1966F. J. LUKETA 3,281,980

PROGRESSIVELY FLOODING TRAWL DOORS Original Filed Aug. 24, 1962 4Sheets-Sheet {5 INVENTOR. ifiAA/K J lam 774 BWMMMMMJ Nov. 1, 1966 F. J.LUKETA 3,281,930

PROGRESSIVELY FLOODING TRAWL DOORS Original Filed Aug. 24, 1962 4 ee s-See 4 INVENTOR. FRANK z/ 1 01 United States Patent 6 Claims. or. 4s 9This is a division of my pending, now abandoned, application Serial No.219,276, filed August 24, 1962, and entitled T-rawl Doors, whichapplication in turn is a continuation-in-part of my now abandoned aplication Serial No. 837,025, filed August 31, 1959, and also entitledTrawl Doors.

The present invention relates to trawl doors having a hollow bodyadapted to afford temporary buoyancy to the door as it sinks in thewater, for the purpose of causing the door to assume a correct attitudeduring setting. The hollow body floods at a slow rate as it descends inthe water, resulting in the boyancy being ultimately dispelled. However,by the time that this happens the door will have assumed a properattitude.

In bnicf, trawl doors according to the present invention each comprise ahollow body having a ballast weight concentrated adjacent its loweredge, and apertures along its upper and lower edges for restrictedcommunication with its interior. The total area of the upper aperturesis substantially less than the total area of the lower apertures. As aresult, air entering and entrapped within the door when out of waterwill tend to buoy up its upper portion while such door is descending inthe water, while the ballast weight pulls its lower edge downwardly. Asthe door sinks the air escapes through theupper edge apertures, and isreplaced by water entering through the lower edge apertures. When thedoor is pulled out of the water after use, the water inside it drainsout through the lower edge apertures. As will be evident, the abovedescribed arrangement avoids superfluous buoyancy of the door in thewater, and superfluous weight when the door is out of the water.

According to the present invention, filler blocks may be dispose-d inthe upper portion of the hollow body and arranged to partially mask theupper edge apertures. Preferably such filler blocks are inherentlybony-ant.

Preferably, the interior of the hollow door is divided into a pluralityof compartments symmetrically related about a horizontal center line,and the door is invertible. These compartments consist of or includeballast weight compartments disposed in'boardly adjacent the two edgesof the door which are horizontally disposed during use. When the door isrigged for use, one of such edges is chosen to be the lower edge of thedoor, and the ballast weight means is put into one or more of thecompartments disposed adjacent such lower edge. When the door isinverted, the ballast weight means is moved across the center line andput into the compartments which are located adjacent the opposite edge,which then becomes the lower edge. -In doors employing filler blocks,compartments are provided for the filler blocks on both sides of thehorizontal center line, so that they can also be moved to the oppositeside of the center line when the door is inverted.

These and other objects, features, characteristics and advantagespertaining to and inherent in the present invention will be apparentfrom the following description of certain typical and thereforenon-limitive embodiments thereof, as illustrated in the accompanyingdrawings, wherein like letter designations and numerals refer to likeparts and wherein:

FIG 1 is a front elevational view of a typical embodiment of trawl doorsaccording to the present invention, such view looking toward thelongitudinally concave anterior surface of such door;

FIG. 2 is a rear elevational view of the door in FIG. 1, such Viewclearly showing the openings in the lower edge portion of the door foradmitting and discharging water, and the openings in the upper edgeportion of the door for admitting and dispelling air;

FIG. 3 is a view similar to FIG. 2, but with the cover and otherportions of the door considerably broken back to illustrate the interiorconstruction;

FIG. 4 is a longitudinal sectional View taken through the same door,substantially along line 44 of FIG. 3;

FIG. 5 is a perspective view of a modified form of door according to thepresent invention, such view being taken from above and looking towardthe posterior side and after end of such door;

FIG. 6 is an exploded perspective view of the door shown in FIG. 5, suchview showing the compartmented interior of the door, including identicalcompartments in the upper and lower regions of the door, so that thebuoyant filler blocks and the ballast weights may be changed to oppositesides of the doors longitudinal center line when the door is to beinverted, and such view also showing the invertible nature of ,thetowing warp connector on the anterior side of the door;

FIG. 7 is a rear elevational view of an end portion of the door of FIGS.5 and 6, with a part of the posterior cover cut away;

FIG. 8 is an enlarged scale fragmentary view of the upper cente-ralportion of FIG. 7; and

FIG. 9 is an enlarged scale transverse sectional view takensubstantially along line 99 of FIG. 7.

Two trawl doors are used, so shaped and oriented as to cause thecurtains of the net (corresponding somewhat to the wings of a standardtrawl net, but much longer, and open of mesh) to diverge widely apartand forwardly, so as to sweep the maximum bottom area. Each such door istowed by a towing wrap W from the trawling vessel, and is connected to anet trailing behind the door by net lines including a sweep line and acurtain line (both designated S in the drawing), which net linestransmit the drag to the net. The doors themselves are generally uprightin use, and during bottom trawling their lower edges ride evenly uponthe bottom, and so the door must be nonbuoyant, and usually is weighted,not only to hold it.down but to maintain it in a generally uprightdisposition as it is set and while it sinks to the bottom, and later toassure that it rides evenly on the bottom.

The door illustrated in FIGS. 14 comprises a body generally designatedby the numeral 1, which in the form shown, as viewed from one side orthe other, is generally rectangular, though with rounded corners. It maysometimes be rounded at its forward end. The door shown, as viewed inplan (see FIGURE 4) is curved or cam'bered from its forward end 10progressively toward its after end 19, although the cambered form is notstrictly essential to other novel features. In other words, the body 1has a concave anterior surface 11 and a complementally convex posteriorsurface 12, and the door has anchorage means for the lines mentionedabove so located as to produce a moment tending to incline the generalplane of the door at a desired fairly large angle of attack withrelation to the direction of For instance, a shackle 2 (FIG. 1) forattachment of a towing wrap W is itself pivotally mounted upon a foreand aft rib 13 outstanding from but close to the anterior surface 11 ofthe door aft of its leading end Ill, but only slightly ahead of thedoors midpoint. Other shackles 3 (FIG. 2) are mounted at the posteriorsurface of the door, these being for connection to sweep and curtainlines indicated,

a for instance, at S in FIG. 4. Preferably the shackle 2 for the towingwrap W is mounted slightly below the longitudinal center line of thedoor; see FIGS. 1 and 3.

The door, whether cambered or not, is preferably formed with rearwardlyinclined lower and upper edge portions or band 14 and 16, respectively,of equal area. These might adjoin one another, at opposite sides of alongitudinal apex line midway between the upper and lower edges, or, asshown, may be separated by an intervening central portion or band 15,which while the door is in use is generally upright. All such bands 14,15, 16 are shown to be of hydrofoil shape longitudinally. The dihedrallyrelated bands 14 and 16, in cooperation with the below-center locationof the anchorage of the towing warp W to the door, already mentioned,afford stability to the door in a manner explained below.

The lower edge of the door drags over the bottom, and should bearthereon evenly throughout its length. The towing warp W is anchored tothe doors anterior or concave face at the shackle 2. This shackle 2, asalready explained, is located close into and slightly ahead of the doorslongitudinal center line of the door. Such a below-center locationproduces a tendency for the upward component of the pull of the towingwarp to tilt the door backwardly about its lower edge, and so countersthe drag of the bottom against such lower edge. As a result the doortends to remain upright as it advances, and desirably can be so arrangedas to tilt rearwardly slightly. The small longitudinal moment arm fromthe anchorage 2 rearwardly to the midpoint of the doors length tends toprevent uptilting of the doors forward end 10 off the bottom, especiallywhen assisted by the location of ballast weights forwardly, as will "beexplained later. The upper dihedral band 16, when the door is tiltedsomewhat backwardly, causes the door, by water reaction, to be stronglyurged downwardly, and therefore it will stay on the bottom more surelywith a minimum of ballast.

Thus there are forces arising from the dihedral disposition of bands 16,14, from the below-center location of anchorage 2, from the lattersshort spacing ahead of the longitudinal midpoint of the door, and fromthe longitudinal disposition of the ballast weights, which cooperate tomaintain the door at the proper angle of attack, yet held down to andbearing evenly along the lower edge upon the bottom, and approximatelyupright as it advances.

Inasmuch as the lower edge bears upon and drags over the bottom, wearoccurs there, and should be absorbed by a protective element. Forexample, a pad 7 of wearresistant rubber is vulcanized or otherwise heldin place upon the doors lower edge, and can be renewed when worn, or asshown in FIGS. 5, 6 and 9, and as is preferable, a complete ring 7aencircles all the edges of the door, and is removably secured in place,so that it is replaceable when worn at both horizontal edges, in themanner disclosed in my aforementioned application Serial No. 219,276.

When the protective edging 7a is employed, the trawler can carry aspare, and whenever one becomes unduly worn, it can be replaced withlittle loss of time, whereas with shoes or the like that are bonded inplace, the door as a Whole must be shipped to a repair station, andreplacement is bound to be expensive, and a cause of delay.

The door is ballasted at its lower edge. While the location of ballastweight longitudinally would be governed by the doors balance, and by anytendency to tilt upwardly its forward endthe aim being to have it bearequally upon the bottom along its lower edgethe towing warp anchored at2 produces some upward component, especially when wave action or thelike tends to jerk and pull the warp taut. Accordingly, it is preferredthat the ballast be concentrated towards the forward end 10 of the doorslower edge. Ballast weight or Weight blocks 6 or 6a are shown, solocated.

Referring specifically to FIGS. -9, it is preferred that the door beformed as a hollow nonbuoyant body 1a, for instance of cast aluminum,covered by a lightweight back plate or cover 17 held in place by thebolts 18. It must, however, be drainable, and is so shown. Preferably,it is provided with transverse or upright ribs 5 and a longitudinal ribor ribs 50. In the form of FIGS. l-4 it is also provided with angularlydisposed bracing ribs 51, which interconnect the anchorage point for theshackle 2 with the anchorage points for the shackles 3. The two latterpoints are interconnected again by a transverse rib or spreader 5, sothat stresses are transmitted between the points of maxi-mum stress in amost direct manner, and are strongly resisted.

The rubber-coated ballast weight 6 shown in FIG. 3 is mounted within acell or cells within the hollow structure of the door, by bolts 60 orthe like, and may be removed and shifted in location, as foundnecessary, upon removal of cover 17.

The door of FIGS. l-4 is not intended to be reversible top for bottom,whereas the door of FIGS. 5-9 is thus reversible. The ballast weights 6ain the latter form are received alternatively in cells within the hollowdoor structure along the upper and lower edges (whichever edge is thenthe lower one), and are secured therein by the bolts 60a, see FIG. 6.

Buoyance is afforded, at least temporarily, to the upper portion of thedoor body in any of a number of ways. In the form of FIGS. 1-4 the cellsdefined by interior dividers 5 and 50 are open, at least restrictedly,to the atmosphere when the door is out of water, by way of holes 17balong the upper margin of the body 1a or its cover 17. Along the lowermargin of the same, drainage holes 17a communicate with the interior.When setting the net the initial few moments in the launching of thedoor are critical, because unless it automatically assumes its uprightdisposition and positive angle of attack it may veer inboard and foulgear at the opposite side. This will require that it be hauled in,cleared, and reset, with consequent labor and loss of time. The locationof the ballast weight at the lower edge, and the buoyance afforded theupper edge by air temporarily trapped there, because it cannot at onceescape through holes 17b, which holes must be regulated as to size, toprovide the intended lag in escape of air, which, being replaced bywater, causes the door to assume its correct orientation as it sinks inthe water. Air escapes somewhat slowly through holes 17b, for reasonsalready given, and the temporary buoyance is dispelled. In consequencethere is no residual buoyance which must be overcome all during use byproviding extra ballast Weights, as must be permanently buoyant meansusually provided along a doors upper edge.

The door in the form of FIGS. 5-9, which is reversible top for bottom,accomplishes a like result in a somewhat different manner. Buoyantblocks 8 fit within cellules n the upper portion of the doors interior,and are held 1n place by the cover 17. Apertures in the horizontaldividers 50a afford communication between drain holes 17a and air exitholes 17b, in cooperation with channels 81 in blocks 8. Suchcommunication is restricted, since the blocks partially mask the holes1712. When the door 1s let into the water the ballast weights and thebuoyant upper space causes it to assume the correct attitude, and as thewater slowly displaces the air within the hollow door, it graduallyloses its buoyance, which now is not needed, and if present would bedetrimental, in that it would require added ballast; see FIG. 23.

The reversible door of FIGS. 5-9 employes a modified form of anchoragefor the towing warp W. Whichever horizontal edge is uppermost, theshackle 2a should be below the longitudinal center line. It must beshifted when the door in inverted. As seen in FIG. 6, the shackle 2a isformed with a pivot sleeve 20a that has a bushing 21a held by a pin 22abetween ears 13b of a bracket secured to the anterior face of the doorbody. The shackle,

2a is located nearer one end of the pivot sleeve 20a than the other end.In the full line position of FIG. 20 the shackle 2a is well below thecenter line C of the door, whereas if the shackle and pivot sleeve areinverted to the dot-dash line position, and the door too is inverted,the shackle is again in the correct below-center location.

Some of the figures of the drawing show an after vane assembly VAattached to the posterior side of the door. This assembly in part formsthe subject matter of my forementioned parent application Serial No.219,276. To the extent that it may be desirable to a clearerunderstanding of the present invention, the disclosure of saidapplication Serial No. 219,276 is hereby incorporated herein by specificreference.

From the foregoing, further modifications, adaptations, and variationsof trawl doors according to the present invention will be apparent tothose skilled in the trawling art, within the scope of the followingclaims.

What is claimed is:

1. A hollow trawl door disposed generally upright in its position ofuse, a weight concentrated adjacent its lower edge, said door havingapertures along its upper and lower e ges for restricted communicationwith its interior, with the total a ea of the upper apertures beingsubstantially less than the total area of the lower apertures, wherebyair entering and entrapped within the door when out of water will tendto buoy up its upper edge when it is dropped into the water, while theweight pulls its lower edge downwardly, until the air escapes throughsuch upper edge apertures, and is replaced by water entering through thelower edge apertures.

2. A hollow trawl door formed with lower holes for admission of water,and upper holes for escape of air adjacent its upper edge with lessertotal area than the total area of said lower holes and communicatingwith said lower holes, whereby the air escapes from the hollow interiorof the door at a limited rate when the door isfirst submerged.

3. A trawl door comprising a hollow body, said body having open air ventmeans admitting to its interior along its upper edge, and open waterdrain means also admitting to its interior along its lower edge andcommunicating with said open air vent means, the said water drain meansbeing of substantially larger total area than the total area of said airvent means whereby the air escapes from said hollow body at a limitedrate when the door is first submerged in the water.

4. A trawl door as in claim 3, and a ballast weight supported adjacentthe lower edge of the door, to maintain its lower edge lowermost.

5. A trawl door comprising a hollow, nonbuoyant body having holesadmitting to its interior at its top and bottom edges, filler blocksdisposed within the upper part of said body and and arranged to mask theholes there, partially, for restricted communication between the holesand the interior space below such filler blocks, and a weight masssupported adjacent the bottom edge of the door.

6. A trawl door as in claim 5, wherein the filler blocks are inherentlybuoyant.

References Cited by the Examiner FOREIGN PATENTS 1,260,072 3/1961France.

26,332 11/1896 Great Britain. 533,121 2/ 1941 Great Britain.

SAMUEL KOREN, Primary Examiner.

W. H. CAMP, Assistant Examiner.

2. A HOLLOW TRAWL DOOR FORMED WITH LOWER HOLES FOR ADMISSION OF WATER,AND UPPER HOLES FOR ESCAPE OF AIR ADJACENT ITS UPPER EDGE WITH LESSERTOTAL AREA THAN THE TOTAL AREA OF SAID LOWER HOLES AND COMMUNICATINGWITH SAID LOWER HOLES, WHEREBY THE AIR ESCAPES FROM THE HOLLOW INTERIOROF THE DOOR AT A LIMITED RATE WHEN THE DOOR IS FIRST SUBMERGED.